Backscattering Models For Ocean Surfaces In Active And Passive Salinity Measurement

The distribution of global SSS(Sea Surface Salinity) is of great importance in our research of climate change, global precipitation and El Ni?o phenomenon. The combined L band active and passive detection can be a better way to revise the influence of sea surface roughness on brightness temperature and then to improve the accuracy of SSS measured. Based on the combined active and passive remote sensing, this thesis has carried on the work as follows:First, based on radiation transfer equation, the mechanism of SSS reversion by sea surface brightness temperature is discussed. The Meissner-Wentz algorithm for brightness temperature correction and CAP algorithm for SSS reversion in Aquarius are studied. The process of the algorithms and the effectiveness and application conditions of their backscatter GMFs are analyzed as well. Finally, the characteristics and difference between the two algorithms are compared.Second, the sea surface roughness is described through statistic parameters. The form and feature of wave spectrum(gravity wave spectrum, capillary wave spectrum) with different generation mechanisms are analyzed. The wind speed and roughness statistic parameters are corresponded based on wave spectrum.Third, the scattering function expressed by tangential field is obtained by Huygens theorem and Extinction theorem, which are deduced from Stokes function. Under this frame, the large scale Kirchhoff Approximation(KA) is derived using tangential plane approximation and the small scale Small Perturbation Model(SPM) is acquired based on series expansion of tangential field. The Integral Equation Model(IEM) with wide range of application is obtained as well when the two scales are both considered. At last, the three models are simulated and their performances in different roughness are analyzed.Fourth, by Integral Equation Model(IEM), the scattering and emission of the sea surface are simulated. First of all, the performance and sensitivity of brightness temperature at different sea surface salinity are analyzed. The simulated results according to the analysis verify the feasibility of salinity reversion by brightness temperature. Then, the behavior of sea surface brightness temperature with roughness is simulated. The results validate that the influence of roughness on brightness temperature cannot be ignored. At last, the performance and sensitivity of sea surface backscattering coefficient with the change of roughness and salinity is analyzed. These further prove the practicability of brightness temperature correction by sea surface backscattering coefficient at various roughness conditions, and then lay the foundation of our future work for high-precision sea surface salinity reversion.